\(6\times\left(\frac{2}{5}\times x+3\right)=\frac{3}{5}\Rightarrow\frac{2}{5}\times x+3=\frac{3}{5}\div6\Rightarrow\frac{2}{5}\times x+3=\frac{1}{10}\)
\(\Rightarrow\frac{2}{5}\times x=\frac{1}{10}-3\Rightarrow\frac{2}{5}\times x=\frac{-29}{10}\Rightarrow x=\frac{-29}{4}=-7,25\)